This invention relates to a bio-absorbable cartilage repair system for regenerating articular cartilage and, more particularly, a system which allows for vascular invasion and cellular migration between the system and the adjacent healthy area of articular cartilage and cancellous bone, thereby resulting in regeneration of the damaged articular cartilage.
Articular cartilage on the surface of bones in joints, most particularly the knee, ankle and hip joints, is susceptible to deterioration caused by injury or disease. This deterioration of cartilage leads to pain and eventually loss of joint movement and more severe pain. As a result, various methods have been developed to treat and repair damaged or destroyed articular cartilage.
Prosthetic devices are often used to replace damaged or destroyed articular cartilage. For example, U.S. Pat. No. 4,627,853 discloses prosthesis which are used for articular cartilage replacement. The prosthesis are prepared by demineralization of a bone segment, the demineralized bone segment serving as a replacement for articular cartilage.
U.S. Pat. No. 5,176,710 discloses a prosthesis for replacing bone material on the articulating surface of a joint. The prosthesis has a specific modulus of elasticity so as to confer stiffness to the prosthesis, and contains concave shapes which are suitable for biologic ingrowth.
U.S. Pat. No. 3,745,590 discloses a prosthesis for the repair or replacement of joints, which prosthesis comprises a body portion, including a stem and ligamentous elements, and allows for tissue ingrowth.
U.S. Pat. No. 5,123,927 discloses a knee prosthesis comprising bone cement containing an antibiotic.
U.S. Pat. No. 4,904,259 discloses a resorbable gel, including ex vivo chondrocyte cells, press fit into a cartilage defect.
U.S. Pat. No. 5,270,300 discloses a scaffold into which cells grow, but without any blood supply from the subchondral bone.
U.S. Pat. No. 5,306,311 discloses a resorbable prosthesis suitable for biologic ingrowth.
PCT Publication No. PCT/WO95/30383 discloses ex vivo proliferated, denuded chondrogenic cells for synthetic cartilage use in surgically repairing cartilage defects.
Although there are several prosthetic devices which can be used in the replacement of damaged or destroyed articular cartilage, prosthetic devices have several disadvantages. For example, cements which are used to attach prosthetic devices to bones may loosen and eventually fail. In addition, fragmented cement can move into the joints and associated lymph tissue and cause inflammation and further damage. Further, cements result in the formation of fibrous tissue between the bone and the prosthesis. Another major disadvantage associated with the use of prosthesis is that the prosthetic device may be larger than the damaged cartilage that needs to be replaced, thereby requiring removal of portions of healthy bone and/or cartilage in order to accommodate the prosthetic device. Hence, the need remains for a system for repairing and regenerating articular cartilage which avoids the problems associated with prosthetic devices.
Another means used to treat damaged articular cartilage is the placement of repair pieces onto the bone, which repair pieces substitute for cut-out pieces of cartilage. For example, U.S. Pat. No. 5,067,964 discloses an articular cartilage repair piece which comprises a layer of non-woven, felted fibrous material which is limp and readily conformable to flat and curved surfaces. The articular cartilage repair piece is attached to the bone, for example, by bio-absorbable screws or pins or like temporary fixation techniques. Fibrous tissue ingrowth eventually surrounds the repair piece thereby causing the repair piece to be permanently attached to the bone. Although U.S. Pat. No. 5,067,964 discloses an alternative method for repairing damaged articular cartilage, it does not disclose any means or method of regenerating damaged or destroyed articular cartilage. Hence, the need remains for a system for regenerating damaged or destroyed articular cartilage, wherein the regenerated articular cartilage is functionally similar to non-damaged articular cartilage.
Commonly owned U.S. Pat. Nos. U.S. Patent No. 5,632,745; U.S. Pat. No. 5,749,874; and U.S. Pat. No. 5,769,899 disclose such a regenerating system and are incorporated herein by reference. However, the regenerating systems disclosed therein have not proved to be entirely satisfactory from the points of view of both the manufacturer and the surgeon installing the same in a patient.
Accordingly, an object of this invention is to provide a system for regenerating articular cartilage.
Another object is to provide a system for regenerating articular cartilage wherein the regenerated articular cartilage is functionally superior to fibrous or fibrocartilagenous repairs and is functionally similar to non-damaged articular cartilage.
A further object is to provide a cartilage repair system for use in regenerating damaged or destroyed articular cartilage.
It is another object of the present invention to provide an embodiment of the cartilage repair system which does not employ cement or non-bio-absorbable prosthetic devices.
It is a further object to provide an embodiment of the cartilage repair system for repairing bone as well where there are injuries to both cartilage and bone.
It has now been found that the above and related objects of the present invention are obtained by a bio-absorbable cartilage repair system for regenerating damaged or destroyed articular cartilage on the joint surface of a bone, which system establishes a chondrogenic growth-supporting matrix between an area of damaged or destroyed articular cartilage that has been removed and an adjacent healthy area of articular cartilage and cancellous or trabecular bone. The system comprises an assembly of a bio-absorbable delivery unit and a porous bio-absorbable insert. The delivery unit is formed of bio-absorbable material and configured and dimensioned to be mounted in both an area of damaged or destroyed articular cartilage that has been removed and an adjacent healthy area of articular cartilage and cancellous bone. The delivery unit has a central body and a plurality of radially extending, flexible support arms projecting outwardly from the central body and configured and dimensioned to support the insert at least partially thereover. The insert is supported by the delivery unit, formed of bio-absorbable material, and establishes communication between the removed area and the adjacent healthy area for a chondrogenic growth-supporting matrix.
In a preferred embodiment, the insert is disposed on the upper, lower, and outer surfaces of the support arms, and the support arms have free ends circumferentially spaced from one another to define areas for receipt of a chondrogenic growth-supporting matrix. The support arms preferably have circumferentially spaced free ends adapted to engage and at least partially spatially stabilize the insert. The support arm free ends may be horizontally or vertically barbed. The central body adjacent a bottom end thereof defines a plurality of outwardly extending flanges.
In a preferred embodiment, the insert has a top, a bottom and a sidewall connecting the top and bottom. The bottom allows vascular invasion therethrough, and the top and sidewall allow cellular migration therethrough by an adjacent healthy area of articular cartilage and subchondral cancellous bone. The insert may include cells to facilitate establishing such communication. The sidewall is preferably polygonal in plan. Each of the delivery unit and the insert preferably essentially consists of completely bio-absorbable material which is ceramic-free and dimensionally stable in synovial joint fluid against expansion due to the absorption thereof.
The system may additionally include retainer means for securing the insert to the delivery unit. The retainer means is secured to a portion of the central body below the insert and bears upwardly against the insert. The retainer means essentially consists of completely bio-absorbable material which is ceramic-free and dimensionally stable in synovial joint fluid against expansion due to the absorption thereof.
Preferably the system additionally includes a porous film formed of bio-absorbable material securing the insert to the delivery unit. The porous film has a central film portion disposed over the insert and a plurality of film fingers projecting outwardly from the central film portion, downwardly and inwardly, under the support arms. Optionally, upwardly barbed retainer means are secured to the central body and bear upwardly against the film fingers. The porous film essentially consists of completely bio-absorbable material which is ceramic-free and dimensionally stable in synovial joint fluid against expansion due to the absorption thereof.
In another preferred embodiment, the insert is a flexible porous film formed of bio-absorbable material secured to the delivery unit. The porous film has a central film portion disposed over the support arms and a plurality of film fingers projecting outwardly from the central film portion, downwardly and inwardly, under the support arms. A retainer means is preferably secured to the central body and bears upwardly against the film fingers. The porous film essentially consists of completely bio-absorbable material which is ceramic-free and dimensionally stable in synovial joint fluid against expansion due to the absorption thereof.
In the latter embodiment, preferably the central body defines an aperture extending longitudinally therethrough, and the insert defines an aperture extending longitudinally therethrough. A retainer means may be secured to the central body and bears upwardly against the insert, the retainer body defining an aperture extending longitudinally therethrough coaxial with the central body aperture. A porous film consisting substantially of completely bio-absorbable material may secure the insert to the delivery unit, the porous film defining an aperture extending longitudinally therethrough coaxial with the central body aperture. When the insert is a flexible porous film consisting substantially of completely bio-absorbable material secured to the delivery unit, the porous film may define an aperture extending longitudinally therethrough coaxial with the central body aperture.
In yet another embodiment, at least a portion of the delivery unit central body disposed below the insert defines flexible legs, the system additionally including means for moving the legs from a horizontally retracted orientation enabling removal of the assembly to a horizontally expanded orientation fixing the assembly in place. Preferably, the flexible legs are resilient, and the moving means is retractable to enable movement of the legs from the expanded orientation to the retracted orientation.
Preferably, the insert consists substantially of a bio-absorbable material selected from the group consisting of hyaluronic acid, polyglycolic acid, collagen, polylactic acid, fibrin clot, periosteal cells, polydioxane, polyester, alginate and combinations thereof, while the delivery unit comprises a bio-absorbable material selected from the group consisting of hyaluronic acid polyglycolic acid, polylactic acid, alginate and combinations thereof.
In a preferred embodiment, the insert includes a repair factor releasably disposed in the insert to assist in establishing the chondrogenic growth-supporting matrix. The repair factor may be a growth factor, preferably one selected from the group consisting of fibroblast growth factor, transforming growth factor beta, insulin, insulin like growth factor, platelet derived growth factor and combinations thereof. Alternatively, the repair factor may be an attachment factor, preferably one selected from the group consisting of fibronectin, RGD polypeptide and combinations thereof, or a cell factor, preferably one selected from the group consisting of stem cells, periosteal cells, and cells containing genes specific for cartilage formation and combinations thereof. Indeed, the repair factor preferably includes growth, attachment and cell factors.
The delivery units of the assemblies are disposed within the bone and the removed area, and the inserts of the assemblies establish the chondrogenic growth-supporting matrix over a substantial portion of the removed area. The insert of the assemblies may be polygonal in configuration and interfitting.
The cartilage repair system preferably includes means precluding relative rotation of the delivery unit and the insert in the delivery unit.
The present invention further encompasses a cartilage repair system adapted to be mounted on the joint surface of a bone to establish a chondrogenic growth-supporting matrix, wherein the system comprises a bio-absorbable delivery unit configured and dimensioned to be mounted on the bone, the unit including a support frame and means for mounting the unit in the bone, and a porous bio-absorbable insert supported by the support frame to provide a chondrogenic growth-supporting matrix. Preferably the support frame is constructed to allow vascular invasion and cellular migration to the insert.
In one preferred embodiment of the present invention, the delivery unit is a subassembly of two separately formed components, one of the components being configured and dimensioned to be mounted in both an area of damaged or destroyed articular cartilage that has been removed and an adjacent healthy area of articular cartilage and cancellous bone, and the other component having a central body and a plurality of radially extending, flexible support arms projecting outwardly from the central body and configured and dimensioned to support the insert at least partially thereover. Preferably, the one of the components defines a longitudinal aperture therethrough and the central body of the other component is configured and dimensioned to at least partially pass through the aperture. The subassembly may be assembled with the insert prior to use. At least one of the components includes means for retaining the components together after assembly, and the subassembly includes retainer means for bearing on a portion of the insert intermediate the two components to lock the delivery unit portion in place.
Additionally, the present invention encompasses a bio-absorbable cartilage repair system comprising an assembly consisting essentially of two delivery units and a single flexible porous insert. The insert is supported by both of the delivery units, is formed of flexible bio-absorbable material, and establishes communication between the removed area and the adjacent healthy area for a chondrogenic growth-supporting matrix. The delivery units are configured and dimensioned to enable them to be disposed along a common longitudinal axis, facing each other, and connected only by the insert for insertion into a patient. The assembly is then unfolded to enable the delivery units to be separately mounted along generally parallel longitudinal axes, side-by-side. Preferably the insert defines a pair of insert portions, each insert portion extending over the top of a respective one of the delivery units, and a connecting portion of reduced width foldably connecting the insert portions together.
Further, the present invention encompasses a bio-absorbable cartilage repair system comprising an assembly of a delivery unit and a porous insert. The delivery unit has a central body and an inwardly compressible plurality of spirally or helically extending, flexible support arms projecting outwardly from the central body and configured and dimensioned to support the insert at least partially thereover. Preferably, the system comprises at least two of the assemblies, each delivery unit being mounted side-by-side such that at least one support arm of one of the delivery units inwardly compresses at least one support arm of the other of the delivery units. The at least one support arm of one unit would overlap at least one support arm of the other unit if at least one support arm were not inwardly compressed.
In a preferred embodiment of the present invention, a top layer of the insert contains a chondrogenic growth-supporting matrix, and a lower portion of the insert contains an osteogenic growth-supporting matrix, the assembly being configured and dimensioned to be disposed with the chondrogenic growth-supporting matrix adjacent a healthy area of articular cartilage and the osteogenic growth-supporting matrix adjacent a healthy area of subchondral cancellous bone, thereby to establish chondrogenic and osteogenic growth-supporting matrices in removed areas of damaged or destroyed articular cartilage and subchondral bone, respectively.
In another preferred embodiment, the delivery unit includes a head portion and a stem portion, the head and stem portions being pivotally joined together, one of the portions preferably defining a ball and the other of the portions preferably defining a socket. Optimally the stem portion defines a ball at a distal end, and the head portion defines a socket at a proximal end, the ball being pivotally maintained in the socket such that the head portion is pivotable relative to the stem portion.